His Dark Materials team promises a 'heart-wrenching,' 'incredibly profound' ending

His Dark Materials is coming to an end with the third and final season coming to HBO this December, and the team behind the fantasy series promises an ending that's just as moving as the books on which it's based.

"This one ends in a pretty heart-wrenching, emotional, but also an incredibly profound way," says executive producer Dan McCulloch, who joined showrunner Jane Tranter and actors James McAvoy and Amir Wilson in EW's New York Comic Con video suite Thursday. "These books, I read them when I was a teenager, still watching the end of the show now, I think they still move me as they did then."

Seasons 1 and 2 of His Dark Materials adapted the events of The Golden Compass (titled Northern Lights in the U.K.) and The Subtle Knife, respectively — the first two novels in Philip Pullman's Dark Materials fantasy series. Season 3 now adapts the finale entry, The Amber Spyglass.

James McAvoy in His Dark Materials season 3
James McAvoy in His Dark Materials season 3

HBO James McAvoy in' His Dark Materials' season 3.

Prophesied child Lyra (Dafne Keen) and Subtle Knife bearer Will (Wilson) must now embark on an adventure to a dark plane, one book readers know quite well. Meanwhile, McAvoy's Lord Asriel returns after being absent for the vast majority of season 2 to wage war against the Authority (i.e. God).

"We had to make good on all the promises of season 1 and season 2 and show the stuff that Coulter and Asriel do," McAvoy says of his and Ruth Wilson's characters. "In the books, you don't really see it. You're told about it a little bit or in hindsight 'hey, there are other things happening over there in the Republic of Heaven with Asriel,' and we had to show a lot more of it. And it was just about making sure that we were still true to who he is and his drives and his impulses and his objectives still bear the actions of what we end up choosing to create in season 3."

"That was always a challenge," McAvoy adds, "because you're inventing stuff and when somebody who's as incredible as Philip Pullman ... you're gonna be held up against his invention, held up against his creation and his imagination and his penetration of themes and ideas. And that's a very high bar that I think we all were collectively aware of."

Watch the full interview in the video above.

Sign up for Entertainment Weekly's free daily newsletter to get breaking TV news, exclusive first looks, recaps, reviews, interviews with your favorite stars, and more.

Related content: